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Differences in toxicity effects between LAN and urea

By FERTILIZER PRODUCTS, Nitrogen, Nitrogen Products, PLANT & SOIL NUTRITION No Comments

AFRIKAANS: Die verskil in toksisiteit tussen KAN en ureum Plant mixtures differ to a large extent in nitrogen (N) composition. Nitrate-N: ammonium-N ratios vary according to raw material contents. The optimum nitrate: ammonium-ratio is close to 3:1 while 100% ammonium-N could impair plant growth and yield (Adriaanse 1990). Some companies use urea-N as the primary N source in plant mixtures. Urea in close proximity to developing seedlings could impair or terminate growth. The band placement of certain N sources away from the plant mixture could also reduce yield. (Adriaanse 2012). Furthermore yield could be reduced by an overall excess of N in the soil. (Adriaanse and Schmidt, 2003). This article focuses on potential negative effects of band placed LAN and urea on germination, emergence, and production of maize and wheat. Plant Population Reductions The application of urea and ammonium nitrate at the same relatively high N rate may result in high seedling mortalities for urea compared to no mortalities for ammonium nitrate (Figure 1). These symptoms are often mistaken for genetically associated poor germination or poor seedling vigour. In addition these symptoms are often wrongly ascribed to damage caused by soil insects or meerkats. The band placement of 100 kg N/ha, 50 to 100 mm directly below maize seed at row widths of 1.5 m, resulted in a plant population loss of 4800 plants/ha with LAN compared to a loss of 13300 plants/ha when urea was used (Figure 2). Reductions in plant population were significantly more with urea compared to LAN at both 75 and 100 kg N/ha (Figure 2). This research illustrates relative differences in toxicity between urea and LAN under very specific conditions but does not imply that band placement of either of these N sources directly below the seed at low N rates is an acceptable practice under all conditions. Yield Loss Reductions in plant population due to the application of high N rates, is an indication of very severe N toxicity effects. Impairment of plant growth and yield loss could occur at much lower N concentrations. In another study where urea and LAN were band placed at planting, at a distance of 10 to 15 cm from the row, at a depth of 10 cm, the yield loss for urea compared to LAN was 20% at 100 kg/ha and 44% at 175 kg/ha (Adriaanse, 2012). Row widths were 1.5 m. Most farmers would probably not have been aware of the fact that urea toxicity had occurred.  The yield at 100 kg N/ha in the form of urea was 5 ton/ha which is in line with the yield potential of the area. No toxicity symptoms were observed on the plants, however a yield improvement of 20% at 100 kg N/ha could have been achieved had LAN been used under the same circumstances. Toxicity Symptoms Toxicity symptoms associated with high rates of both urea and LAN applications would probably result in yield loss due to high N concentrations in the soil. In contrast, scorching of leaves associated with spreading of N sources over leaf…

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Limestone Ammonium Nitrate - LAN(28)


By FERTILIZER PRODUCTS, Nitrogen Products No Comments

All figures quoted should be considered as a typical product analysis and may vary due to manufacturing process and raw materials. PHYSICAL PROPERTIES A light / dark grey granular product. Particle shape typically spherical to oblong. Particle size distribution typically ranging from 2.0 – 5.5mm. Critical Relative Humidity @ 30ºC: 59.4 – 65, variance is dependant on chemical stabilisers and coatings used in the production process. Critical Thermal Cycling temperature: 30 – 35ºC; manufacturers specification is normally printed in the bag. Store in a cool dry shed out of direct sunlight. CHEMICAL PROPERTIES 28% Nitrogen (N). N concentration may not exceed 28% in compliance with the Explosives Act (Act 26 of 1956). 14 % N in Nitrate (NO3–) form and 14% N in Ammonium (NH4+) form. Ca content: 3.95 – 4.8% Mg Content: 1.6 – 2.6% Acidification index: 1.12 kg pure lime/kg N or 0.32kg pure lime per kg LAN Salt index: 84 (versus Sodium Nitrate @ 100) AGRONOMIC BENEFITS The N in LAN is immediately available for plant uptake. Research has shown that the 1:1 ratio of Ammonium – N to Nitrate – N as supplied by LAN is the ideal ratio for plant uptake in maize production. LAN contains calcium and magnesium and is less acidifying to the soil than other forms of N. LAN is less prone to N losses through leaching and volatilization than urea. Compatible for blending with MAP, Potassium Chloride, Potassium Sulphate, Potassium Nitrate and Ammonium Sulphate. Please note: Consult a qualified person (Act 36 of 1947) for specific applications / recommendations.  

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